The invention relates to a device for exchanging heat, in particular for use in motor vehicles and in particular for use in motor vehicle air-conditioning systems, Such devices are used, for example, as condensers and evaporators in motor vehicle air-conditioning systems.
The present invention will be discussed with reference to motor vehicle air-conditioning systems, although it should be pointed out that the device for exchanging heat may be used in other air-conditioning systems or for the transfer of heat between two media.
Such devices for exchanging heat are already known, and are used in particular for the air-conditioning of a passenger compartment in a motor vehicle.
Only incombustible coolants are currently used in these air-conditioning systems, since combustible coolants increase the safety risk for people in the motor vehicle passenger compartment owing to the potential danger of explosion. Such coolants are in particular coolants which absorb heat by evaporation at a relatively low temperature and a low pressure, and release heat by liquefaction at a high temperature and a high pressure.
Coolants, for example conventional coolants such as R22 (chlorodifluoromethane), are generally used at present in air-conditioning systems. In even older systems, the coolant R12 (dichlorodifluoromethane) is still found, although its use in cooling systems and air-conditioning systems has been banned for a long time. Since the year 2000, the same has applied to the coolant R22.
The banning of other coolants is also under consideration, for example R134a, so there is an incentive to use alternative coolants.
Such coolants may, for example, be substances or substance compositions which have CO2 as at least one component.
It is an object of the present invention to provide a device for exchanging heat which makes it possible to use alternative coolants and, at the same time, improves the efficiency and economic viability of such apparatus.